Nematicidal efficacy, enhanced degradation and cross adaptation of carbosulfan, cadusafos and triazophos under tropical conditions

Abstract

Nematicides need to be applied in each cropping season but repetitive applications can reduce their persistence and efficacy due to the unpredictable phenomena of enhanced biotransformation and cross adaptation. Experiments were conducted to ascertain the number of times the nematicides carbosulfan, cadusafos and triazophos can be applied effectively in the field. Incubation studies checked their degradation rates and cross adaptation and bioassays assessed their efficacy against Meloidogyne incognita infecting Solanum lycopersicum. Monitoring nematode populations at the middle of seven consecutive tomato crops following nematicidal treatments at a recommendable rate of 1.0 kg a.s. ha −1 revealed a linear decrease in efficacy with successive seasons. The chemicals remained effective up to the fourth application when 53-62% reduction of M. incognita in soil was still achievable, which decreased significantly to 14-33% by the seventh application. The nematicides were more effective against endoparasitic (M. incognita and Rotylenchulus reniformis) than ectoparasitic (Helicotylenchus dihystera, Hoplolaimus indicus and Tylenchorhynchus vulgaris) nematodes. Bioassays revealed 13-18% more invasions of second-stage juveniles of M. incognita into roots of tomato grown in soil pre-treated seven times with nematicide than in similar soil with no history of nematicide use; invasion and soil population were positively correlated. Root galling of field-grown tomato increased from the first to the seventh application. In bioassays, tomato root galling was greater in unsterilised field soil (1.4-2.1) than in similar soil/sterilised soil (1.0) compared with 2.4-2.9 in untreated control soil. The decrease in efficacy was attributable to accelerated microbial degradation of nematicides due to repeated use in each cropping season. Carbosulfan, cadusafos and triazophos exhibited a half-life (t 1/2 ) of 14, 20 and 27 days in soil with no history of nematicide use, whereas the t 1/2 was 6, 13 and 9 days in soil pre-treated seven times with nematicides and 28, 28 and 32 days in unsterilised soil, respectively. In cross adaptation studies, carbosulfan exhibited a t 1/2 of 7-9 days in soil pre-treated seven times with cadusafos and triazophos. The t 1/2 of cadusafos (22 days) was not affected in carbosulfan-treated soil but was affected (13 days) in triazophos-treated soil. Triazophos had a t 1/2 of 20 days in carbosulfan-treated soil and a t 1/2 of 8 days in cadusafos-treated soil. These results indicate that carbosulfan, cadusafos and triazophos can be applied effectively to the same field at least four times without decrease in efficacy due to accelerated biotransformation. Rotation of nematicide from different groups can be used in long-term nematode management strategies to avoid accelerated degradation and/or cross adaptation.

Peristence behavior of Carbosulfan in Brinjal (Solanum melongena L.) Forage

“…22 The carbosulfan residues persevered in chickpea plant parts (roots and shoots) over 90 days but were in trace in seeds. 23 Usually, brinjal leaves as cattle feed will be harvested after the fewharvests of brinjal fruits and there will not be produce anymore. The first harvest of brinjal leaves after spraying was on 14 th day, were below the maximum permissible limit at the recommended dose of 250g.a.i.ha -1 and considered a very meager amount of 2.07 and 5.09µg g -1 of residues was detected.…”

Evaluation of bio-agents, synthetic insecticides and organic amendment against the root-knot nematode, <i>Meloidogyne</i> spp. in cardamom [<i>Elettaria cardamomum</i> (L.) Maton]

“…Therefore their usage has been banned or restricted in many states including Kerala (Narayana et al, 2018). However, a moderate to short persistence of insecticides in soil with a half life of 1-8 weeks in temperate (Meher et al, 2010) and 1-3 weeks in tropical environments (Meher and Sethi, 1992;Meher et al, 2010) is essential. Considering these into account, the insecticides such as cartap hydrochloride, carbosulfan, chlorpyriphos (Wiratno et al, 2009) etc.…”

Enhanced Degradation of Residual Cadusafos in Soils by the Microbial Agent of Cadusafos-degrading Sphingobium sp. Cam5-1

“…현재 사용되는 다양한 살충제 중 유기인계 살충제인 카두 사포스(CAS No. 95465-99-9)는 토양에 서식하는 해충과 선 충에 강한 독성을 나타내며 방제할 수 있는 해충의 적용 범위 가 넓어 국내외 감자, 당근, 고추 등 다양한 농작물을 재배하 는 농가에서 광범위하게 사용되고 있다 [5,6]. 하지만 과도한 카 두사포스 사용은 해충 저항성 증가와 아세틸콜린에스터 분해 효소(acetylcholinesterase) 억제로 인해 분해되지 않고 생체 내에 농축된 아세틸콜린(acetylcholin)은 신경 독성, 폐 질환 가능성 등의 인체 독성이 보고된 바 있다 [7,8].…”